1. Field of the Invention
The present invention relates to a method of removing hydrous silica from bentonite by employing a sodium compound and the irradiation of an ultrasonic wave.
2. Description of the Related Art
Since the bentonite has properties more excellent than those of other minerals in a cation exchange capacity, a caking ability, hydration, and swellability, the bentonite has been used as a binder in a casting industry using a caking property, a civil engineering work material using the swellability, or pesticide additives. Recently, the bentonite has been spotlighted as organic-inorganic nano-composites. In addition, the bentonite shows an increasing trend of the demand in chemical industrial fields including paper, paint, water treatment, and polymer industry which are novel uses based on mineralogical properties of the montmorillonite contained in the bentonite. In order to use the bentonite, the montmorillonite contained in the bentonite is selectively and essentially separated and recovered from the bentonite.
Meanwhile, since a natural bentonite material contains quartz, zeolite, micas, kaolinite, illite, gypsum, or calcite as impurity minerals in addition to montmorillonite which is a main component, the impurity minerals serve as various limitations when the bentonite is used. In addition, impurity minerals intercalated into the bentonite mineral are variously structured depending on the type of a geological change, which is applied to the bentonite mineral in the time of creation of the bentonite mineral, and surrounding mineral environments. In addition, the particle size of a main bentonite mineral, which has the property of a clay mineral in fine particle size, varies depending on the type of surrounding minerals, and the type, the mixing degree, and the distribution characteristic of surrounding impurities.
As schemes to separately select the montmorillonite mineral among bentonites, there are a screening separation scheme to make an ore solution by adding water to bentonite ore, to scrub the ore solution in an agitator by the rotational force of an impeller, and to make the ore solution pass through a sieve having a predetermined size to recover fine particle products, a levigation scheme to mix the bentonite ore with water, to agitate the mixture, to carry floating products into a water stream, and to recover the floating products, and a cyclone scheme to make the ore solution pass through a cyclone to recover only the fine particle product. However, even though the above methods have effects of separately selecting the montmorillonite contained in the bentonite, the montmorillonite mineral is recovered at a lower recovery rate, and only the pure montmorillonite may be hardly recovered. Since the scrubbing process requires a great amount of time and energy, and the separation process requires a great amount to be added, the dehydration and the post-treatment processes are complicated, so that the process cost may be increased.
When the bentonite having a main component as montmorillonite is applied to a human body through cosmetics, foods, or medicines, many diseases, such as cancer, may be caused due to hydrous silica contained in montmorillonite. Accordingly, a method of removing the hydrous silica contained in the bentonite is required.
As a prior art, there is disclosed Korean Unexamined Patent Publication No. 10-2001-0079473 (published on Aug. 22, 2001) entitled “Bentonite (or montmorillonite) Containing Numerous Types of Colloidal Trace Minerals”.